1. Field of the Invention
The present invention relates to a fan control apparatus, and more particularly to a fan control apparatus that controls a fan that is rotary driven by being supplied with a fluid and serves to generate a propulsion force of a flying object.
2. Description of the Related Art
A propulsion force for causing a VTOL (Vertical Take-off and Landing) apparatus to fly has conventionally been obtained by supplying the air by an bleed gas turbine engine and rotary driving a fan. For example, Japanese Patent Application Laid-open No. 2005-125976 discloses a VTOL apparatus having a transfer system of a high-pressure gas type. With such configuration, a drive source takes in the air from an air suction port and compresses the air with a compressor. The compressed high-pressure gas is transferred through a pipe and blown onto an input shaft of the fan to rotate the fan. Based on the fail-safe approach, two drive sources of identical configuration are installed at the VTOL apparatus.
However, in such a VTOL apparatus having two engines, one engine sometimes fails and the so-called OEI (One Engine Inoperative) state is assumed. In the case of such OEI, the revolution speed of the normally operating engine and the turbine inlet temperature are increased over those of the rated output to compensate the insufficient fan drive power. However, immediately after one engine fails, the revolution speed of the normally operating engine is low. As a result, when the required output abruptly increases, a surge or the like occurs, the engine is overloaded, and there is a risk that even the engine that has not failed will not be able to operate normally.